Ground effect flying boats (GEFB) or ground effect flying vessels (GEFV) differ from conventional seaplanes in that they are specially engineered to fly at or near the surface of the water, where their speed and the deflected airstream at the rear of their wings produces a ground effect or air cushion which substantially increases lift and allows flying with reduced engine power and low fuel consumption.
Such GEFVs may also be known as flarecraft.TM. because in aviation the final phase of landing through ground effect is called "flare". Flarecraft.TM. is a trademark of the Flarecraft Corp. of West Germany. Such GEFVs may also be able to flare over flat ground, such as beaches, marshes, deserts, icy lakes and rivers, icy polar zones, and the like, where ground effect may be produced.
When GEFVs fly exclusively over the water (lakes, rivers, oceans) and at a low altitude in surface effect, they are considered as boats and vessels and, as such, are regulated by the Marine and Coast Guard Administration.
GEFBs and vessels were experimented with for several decades, but their use was not widely popularized. Only recently have they awakened interest after realization that the Soviets have successfully built such crafts of all sizes, from single seat to 300 passengers and more, chiefly for military uses.
The advantages of GEFVs are numerous:
1. Considerable reduction of drag as soon as the GEFV is airborne, compared to a conventional vessel in the water, which has a density 800 times that of air. PA1 2. Reduction of the engine power of 2 times and more compared to that needed by conventional seaplanes (which, when flying at higher altitudes, do not benefit from the increased lift of ground effect). PA1 3. Comfort of passengers is increased with a smooth flight in the air, compared to the roughness of boats, and even compared with big vessels in the sea or large windy lakes. PA1 4. Cruise speed is considerably higher than that of the conventional sea vessels, even in quiet weather. PA1 5. Security is increased compared with aircraft because of the ability to water land instantaneously at any moment in case of engine or equipment failure or other sudden problem on board. A GEFV need not search or try to reach a convenient landing airport. PA1 6. There are no limits of runway length, nearby tall buildings, or cross winds on takeoff or landing, as with conventional airplanes or airports. The wide extension of the water field allows orientation of the vessel to a headwind which is beneficial to reduce takeoff speed. PA1 7. There are no problems in crossing over bridges or over harbor zones if necessary, because at such moments, with additional engine throttle, A GEFV may be able to fly over the top of the ground effect zone, with fuel consumption momentarily increased to clear the obstacle. PA1 8. The ability to fly, in flare, without refueling, two or more times the distance of conventional aircraft or seaplanes of the same size are able to fly. This is of interest for civilian uses, and also for the military and Coast Guard to be able to roam coasts for extended periods of time and oceans to effect surprise due to the low radar detection due to the proximity to the water. PA1 9. The cost of construction is cheaper, not only for small flying boats, but also for big oceanic and intercontinental vessels. At low altitude, there is no need for expensive pressurization systems, wing defroster equipment, sophisticated instruments, and certifications which are a must for the security in conventional aircraft.
Because of all of these and other advantages, GEFVs are of interest not only for small boats for recreation and fishing, and the like, but moreover for the intercontinental air transport companies which could substantially lower the price of such transport using GEFVs. It appears which for certain merchandise and freight, the cost of the transport with large cargos would compete with conventional marine ships, not only for reduced fuel consumption, but also for the reduced crew needed and the speed of merchandise delivery.
The former Soviet Union built numerous types of GEFV of all sizes from single seat to large capacity, chiefly designated for military uses. Today, Russia and the USA are both building such craft. Other countries are projecting building larger craft on the order of 1,000 passengers or more.
But according to research performed by the present inventor, it appears that actual building projects unveiled have undervalued some very important inconveniences. These projects do not seem to have addressed defects of GEFVs which are various and of great importance.
Sudden squalls, turbulence, and gusts are very dangerous because they are invisible and very frequent on oceans and large lakes, and even close to permanent in various zones of the world. Such wind disturbances may blow not only horizontally, but also vertically (e.g., wind shear), usually downward when near the surface of the water. Not only a small GEFB may be suddenly projected down over the water's surface, but the same may occur with an enormous GEFV.
The same turbulence also exist higher in the sky (although not so frequently) and there, even a big aircraft may suddenly lose hundreds of feet of altitude. At higher altitudes, however, such wind turbulence may not be a problem because the pilot has space and time enough to reestablish a normal flight. Such is not the case with a GEFV so near the water.
This danger is very serious because the impact with the water occurs within a fraction of a second (also because of the cruise speed of the craft), before the pilot has had time to pull the steering yoke to maintain altitude. The reaction time of an unwarned person is around 1/10th of a second, and at this time, even a light and slow GEFB is already crashed on the water's surface.
Such a crash happened in 1955 to an enormous US seaplane prototype Martin 275 designed to roam the oceans and refuel from submarines, powered by four Allison J71 Jets of 13,000 pounds of thrust each. This seaplane was flying at low altitude over the Potomac River, near Washington, D.C., when a sudden gush pushed it nose down into the water, killing all crew aboard. We know today that such a crash (and likely several others) occurred with a Soviet "Orlyonok" (small eagle) GEFV in the Caspian Sea with 150 military persons aboard with no survivors.
It is also noted that this same danger exists with the small agricultural aircraft sprayers which fly near and over crops. They generally do fly higher than the beneficial ground effect because these pilots know the dangers of these invisible and sudden gusts. Despite all their precautions, according to statistics, this activity suffers the highest rate of mortal injuries in small aviation aircraft, although these pilots have generally many hours of flight and much more experience than a GEFE sport enthusiast pilot would have who only flies occasionally.
Other dangers exist with the actual building projects of some Asiatic and Oceanic enterprises, also inspired by the soviet "Orlyonok" and "Ekranoplan" GEFVs, which have a low, strong and tight wing transversely fitted under the hull bottom and floats into the water at the same time as the hull.
In some contemporary GEFV designs, only the extremities of the "V" inverted wing touch and float in the water. In other GEFV designs, the wing tips are very near over the water surface which is also dangerous. If at the last second before watering, a sudden gust would incline the wing's span it would be very hazardous for a pilot (even an experienced one) to recover the exact horizontal wing level even with the help of ailerons.
Even if the craft could respond so quickly, it might be possible that the pilot would give too much counter inclination; and in which case the other wing tip would touch the water first and the possibility to make a water loop (e.g., ground loop on the water, or "water loop") on that side. Such a water loop could tear a wing from the craft on impact.
The second Martin 275 prototype identical to the one which crashed nose down by a sudden descending squall into the Potomac River suffered such a water loop. These two enormous seaplanes were identical, with a wing in an inverted "V" shape, where only the two tips were floating in the water at the same time as that of the hull. After this second accident, the program for industrial construction was abandoned.
If such waterings (i.e., landing on the water, or "watering") are hazardous with experienced pilots of the US Navy Seaplane Strike Force, it would also be hazardous with civil airline pilots, and even more hazardous with sporting pilots.
It is a fact that gyroscopic and electronic devices (quicker than the human reflex) could react instantaneously, but because of the force of inertia due to the span length, likely the correct horizontal level would not be obtained before contact with the water. Moreover, by watering with strong wind and waves, even with a perfect horizontal wing span, a wing tip could be situated at the last instant over a hollow, while the opposite wing tip could encounter and contact the top of a wave, and cause a water loop.
It seems unlikely that electronic equipment could suppress this problem. Some prior art devices claim the use of a skate-shaped wing tip which is supposed to slide over the water. However, the Martin 275 was also so equipped and the device did not prevent the craft from making a water loop. Because of the distance from the wing tip to the general center of gravity of the craft (situated in the hull), when a wing tip encounters resistance, it is multiplied by the length of the lever arm, and due to its length, the resulting force is enough to produce a water loop or seriously damage or destroy the craft.
Another problem with a GEFV is the considerable extra power needed only for the short time during take off. Such extra power is required to overcome the considerable drag of the transverse hull bottom step which is used (also in seaplanes) to produce water turbulence under the hull, and to prevent the waterstream from sticking on the bottom and thus make take off easier.
The extra power needed for take-offs in conventional GEFVs is a very serious handicap because one of the chief advantages of the GEFV is to be able to fly with low power engines. Once airborne the hull step continues to produce in the air the same turbulence and drag, which reduces cruise speed and increases fuel consumption. Such turbulence is a chief reason why a seaplane is slower than a land-based aircraft and why likely seaplane use was discontinued for oceanic transportation of people and freight.
Other dangers would be the possibility, in darkness or fog, to run into a large marine ship which may not have been seen by radar. To avoid this danger, the ideal solution would be to increase the height of the ground effect to allow the craft to fly higher. Some patents claim the use of flaps which are permanently louvered to send a deflected airstream more abruptly towards the water surface and increase the height of the air cushion.
These same flaps are used in aviation, chiefly for landing to increase lift and reduce speed, and effectively this system is very efficient and useful for such purposes. However, such flaps are always retracted in cruise flight because of the drag which would reduce cruise speed.
Another danger is the possibility of entering into a spin configuration near the water, because at this low altitude, there is not enough space to reestablish control.
Another difficulty with the GEFV (and with seaplanes also) is watering in strong wind and waves. Despite the reduced watering speed (due to the increased headwind), it is dangerous to encounter a moving mass of waves because their speed, added to the reduced speed of the craft, could cause a shock which could split the prow of the hull.
Another important danger for small and large GEFV alike is encounters with fog or rain (very frequent at some latitudes) where a pilot could not see the water surface (the same also occurs at night). In such situations, a crash with the water surface may be difficult to avoid.